On Aug. 21, the tunnel boring machine S36 broke through at Palam Station, 27 days after its twin S37 did the same, completing the last drives on Contract CC-34 of Delhi Metro Phase-III. With this, the contractor has bored a total of 3.6 km by using TERRATEC TBMs.
The breakthrough ceremony was held in presence of the project owner, Delhi Metro Railway Corp., and the contractor, a joint venture between Hindustan Construction Co. Ltd. of India and Samsung Engineering & Construction Group of Korea.
The contractor selected TERRATEC to design and manufacture two 6.52-m OD EPB TBMs with a traditional soil configuration, equipped with a spoke-type cutterhead with a 57% opening ratio. The machines were nicknamed “Jantar” and “Mantar” to remember the Indian gigantic instrument created in the 18th century to measure the time of the day.
The boring of the first stretch started in August 2014 from Vikaspuri Shaft and broke through near Kerala school, where a train cross-over has been planned for this Metro Line, completing a short drive of 219 m. From there both TBMs were dragged 110 m through the cross-over area to start boring a second drive of 354 m to Janakpuri Station. On this drive, The TBMs passed beneath the existing Janakpuri elevated metro station. The distance between the tunnel wall and foundation piles of the existing metro station was only 3 m.
All the stretch between Vikaspuri and Janakpuri stations went under moderate water pressure condition up to 2 bar. The geology was composed of very wet silty clay and sandy soil typical of Delhi. Both TBMs passed underneath residential areas. By using accurate settlement control, the contractor kept settlement within less than 1 cm in those critical zones.
The final stretch of the project for TERRATEC TBMs went from Dashrathpuri to Palam Station. The twin 1,224-m long drives passed through very dry soil. In this zone, the contractor used the foam injection system on the TBM cutterhead to condition the muck. The TBMs went beneath the Palam flyover where the distance between pillars and TBMs was less than 4 m. On this last stretch, the contractor maintained weekly advances up to 120 m per week, allowing the tunneling work to be completed on time.
TERRATEC has deployed a total of eight Tunnel Boring Machines which so far have excavated over 12 km of metro tunnels for different Contracts on Delhi Metro Phase III. All tunneling works will be completed by beginning of 2016.
The breakthrough on CC-34 followed closely on the heels of the completion on CC-07 drives. On Aug. 3, TERRATEC’s S23 TBM completed excavation on the upline from the Kashmere Gate Station to the Lal Quila Station. This is part of the extension of the Central Secretariat corridor to Kashmere Gate via ITO. The breakthrough ceremony was held in the presence of contractor representatives from the joint venture between Metrostroy O.S. of Russia and ERA Infra Ltd. of India and client DMRC.
This TBM was lowered at Kashmere Gate shaft on Dec. 6, 2014, and after assembly of the TBM below the ground the initial drive began on Dec. 26, 2014. The maximum depth of the tunnel is 16 m below the earth’s surface.
The TBM is a 6.61-m OD EPB. It has been specifically designed for the conditions of this project and integrates leading-edge features such as the 900-kw VFD electric driven cutterhead, a versatile design of the cutting tools that are interchangeable with using up to 33 number 17’-in. roller disc cutters, the active type articulation for the shield, and the tail’s built-in 2-liquid backfilling system.
The JV uses a total of two TERRATEC TBMs for the execution of the tunneling works between Jama Masjid and Kashmere Gate Stations. The TBM emerged at Lal Quila Station site after making a 1,351-m long tunnel from Kashmere Gate Station. A total of 967 rings have been inserted concurrently along with the tunneling process. Another TBM is working on a 1,356-m long tunnel on the down line.
The tunnel passes beneath the existing Kashmere Gate elevated Metro Station. The stations at Kashmere Gate and Lal Quila are also being constructed by the same contractor using the cut-and-cover. The distance between the tunnel wall and foundation piles of the existing metro station is 1.2 m. An extensive instrumentation and monitoring regime was put into place.
Under the Delhi Metro Phase-III plan, the Violet Line is being extended from its current terminus to meet the Yellow and Red Lines at Kashmere Gate Station. This will offer an alternative route between Central Secretariat and Kashmere Gate Stations, easing crowds on the heavily-used Yellow Line.
TERRATEC has deployed a total of eight TBMs, which so far have excavated over 12 km of metro tunnels for different contracts on Delhi Metro Phase III. All tunneling works will be completed by beginning of 2016.